<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>

    <style>
        /*id选择器*/
        #d1{
            color:red;
        }
        /*类选择器*/
        .c1{
            color:green;
        }
        /*分组选择器*/
        #d1,.c1,h3{
            background-color: lightskyblue;
        }
    </style>
</head>
<body>
<div id="d1">div1</div>
<div>div2</div>
<div class="c1">div3</div>
<span>span1</span><span>span2</span>
<span class="c1">span3</span>
<h3>我是h3</h3>
</body>
</html>
